Pericardial access for cardiac ablation is often accompanied by the need to place a sheath in or around the pericardial space. A radiofrequency (RF) ablation catheter may be deployed in the sheath. The sheath may also provide for irrigation. The purposes of such irrigation may include, but are not limited to, controlling localized temperature increases to thereby allow the delivery of deeper lesions.
It follows that during pericardial ablation, fluid may accumulate inside the pericardium to an undesirable degree. Furthermore, accumulation of pericardial fluid may be from other causes not related to irrigation from the sheath. These include, but are not limited to, irritation in the pericardial space causing increased pericardial fluid product, application of cryoablative energy that increases fluid volume in the pericardial space, or bleeding as a complication of perforation of either the epicardial coronary vessels or of the cardiac chambers.
Accordingly, pericardial ablation may involve removing accumulated fluid by any of various methods. First, fluid removal may be performed by removing the ablation catheter, inserting another catheter into the sheath, and then removing the fluid via the second catheter. Second, fluid may also be removed by utilizing the space around the ablation catheter. The first method of removing fluid requires multiple withdrawals and reinsertions of the ablation catheter. The second method of removing fluid is limited by a markedly limited amount of residual lumen (in the sheath) that is available for fluid flow in addition to holding the ablation catheter. Thus, there is limited capability to remove fluid while the ablation catheter is in place. Furthermore, use of a sheath that is “oversized” relative to the ablation catheter is clinically unwise during pericardial access. This is true because such sheathes require a larger puncture considering the sheath must have a greatly enlarged diameter to allow any appreciable fluid flow about the catheter.